In the manufacture of most molded products, adhesion between the mold and the material being molded often causes the problems of poor product release from the mold and a product with a non-uniform matte finish. This is particularly so in the production of cosmetics and especially so with lipstick production. Because such a non-uniform matte finish reduces a lipstick's aesthetic appearance, efforts have been made to provide lipstick with a shinier and more uniform (i.e., a more cosmetic) appearance.
One common technique for eliminating the nonuniform matte finish on molded lipstick involves "flaming" the lipstick after it has been removed from the mold. While flaming has been found to improve the finish of the lipstick, the degree of improvement is limited. Thus, ultra-glossy or "wet look" finishes cannot be achieved by flaming. Moreover, some lipsticks, such as those with molded indicia or those with low melting temperatures, are not suitable for flaming.
A second method for achieving a glossy finish is to coat the surface of the cosmetic product with silicone or a silicone derivative. Because of various problems, including absorption of the coating by the product and poor uniformity of product gloss, a method has been developed to increase adhesion between the coating and the cosmetic material and to prevent absorption of the coating into the cosmetic material. This method disclosed in copending patent application Serial No. 07/296,230, filed Jan. 12, 1989 and now U.S. Pat. No. 4,978,524, still requires additional post-molding processing to achieve a uniform high-gloss surface.
Mold adhesion also necessitates frequent cessations between molding cycles to allow workers to clean, replace or otherwise maintain a mold.
Thus, there is a real need for an alternate production method which improves the finish of the molded lipstick without requiring additional steps in the production process beyond the molding itself.
Methods of reducing work stoppage to clean or repolish molds have primarily focused on the application of releasing agents such as silicone derivatives, Teflon spray, carbon or molybdenum disulfide after every few mold cycles. These releasing reagents have the disadvantages of requiring repeated application as well as releasing potentially harmful vapors. Teflon cannot be used to permanently coat any mold for which there is a requirement that the product have a smooth surface because Teflon gives a granular texture to any surface to which it is bonded.
All of the above-mentioned adhesion-related problems are applicable to molds of any composition, but are especially relevant to molds which could be made primarily of a polymer material. Polymer molds can be made less expensively, perhaps to the point of disposability, than metal molds. However, due to the high adhesion between polymers and the materials in lipstick or other molded cosmetic products, it has been impractical to use polymer molds in the cosmetic industry. There is therefore a need for polymer molds to be pre-treated in a manner which greatly reduces the adhesion between the molds' walls and the material being molded.